The Unavoidable Flashbulb

In staying with my "Rear Window" buzz after last night's showing at the Texas Theatre, I do have to concede that there's one scene I've always had a problem with. It occurs near the end where Jimmy Stewart and Raymond Burr, the across-the-way wife-murderer come face-to-face in Stewart's apartment. 
-

The rotund Burr, after poking around with a few questions, then slowly walks across the dark apartment like Frankenstein in one of those Hammer Horror films. Stewart, a photographer, stuns him four times with flashbulbs before he eventually arrives. 
-
The scene is extremely well executed by Hitchcock and Robert Burks, effectively simulating the temporary blinded vision that can be caused by an ultra-bright light, but I've always thought that anybody in their right mind, after one or two flashbulbs to the eyes, could simply shield or close their eyes and avoid being stunned by the flash. 
-
This goes back to my Frankenstein analogy - it's like Burr is a witless, unintelligent monster with the mind and maturity of a 9 year-old. He just keeps on lumbering towards his foe without any regard for himself.